The present invention relates to a poppet valve directly used for supplying working fluid such as source gas in physical and chemical machines and the like or used for reducing pressure in a vacuum chamber using such source gas and more specifically relates to a poppet valve with a heater and constituted such that adhesion of a product from the working fluid to a valve member and the like is prevented by the heater.
In a manufacturing apparatus of a semiconductor, for example, high-temperature source gas is used for chemical treatment such as etching carried out in a vacuum chamber and a poppet valve is used for supplying the source gas or for reducing pressure in the vacuum chamber. However, a product is likely to be precipitated from the source gas when a temperature of the source gas becomes low and the product adheres to a valve member for opening and closing a flow path to reduce an opening/closing accuracy. Therefore, it is important that such a poppet valve is constituted to be able to prevent precipitation of the product from the working fluid, adhesion of the product to the valve member, and the like.
Therefore, conventionally, a poppet valve with a heater in which an inside of a casing, a valve member, and the like are heated by a heater to prevent adhesion of a product has been proposed. There is one disclosed in Japanese Patent No. 3005449 in which a band heater is wound around an outer face of the casing and a rod-shaped heater is mounted to a valve member for opening and closing a flow path through an inside of a hollow rod extending from the valve member. There is also one disclosed in Japanese Patent No. 3012831 in which a rubber heater is mounted to an outer face of a casing and another heater is mounted to an outer periphery of a retaining body in a shape of a cylinder integral with a valve member.
However, if a large heater with such a large heat capacity as to be able to sufficiently heat the valve member on its own is mounted to the valve member which is a movable member like in the above-described conventional poppet valves, weight of the valve member is increased by the heater. As a result, a driving force required for opening and closing has to be increased and responsiveness is likely to reduce. Therefore, it is desired that the heater is not directly mounted to the valve member but is disposed at a place other than the valve member where possible to be able to always heat the valve member by the heater irrespective of an operating position.
It is a technical object of the present invention to provide a poppet valve which has a heater for heating a valve member and in which the heater is not directly mounted to the valve member but is disposed at a place other than the valve member to be able to always heat the valve member by the heater irrespective of open/closed positions.
To achieve the object, according to the invention, there is provided a poppet valve with a heater, the valve comprising: a valve casing including a first main port and a second main port, a flow path connecting both the main ports, and a valve seat provided in the flow path; a cylinder connected to the valve casing; a poppet-type valve member provided in the valve casing to open and close the valve seat; a rod having a tip end portion connected to the valve member and a base end portion on an opposite side and extending into the cylinder; a piston disposed for sliding in the cylinder and connected to the base end portion of the rod; a heat-generating member disposed in a fixed position in the valve casing and having at its tip end portion a heat-transfer face with which the valve member comes in contact in an open position; a heat-transfer member disposed for expansion and contraction in response to an operation of the valve member between the heat-generating member and the valve member to constantly transfer heat from the heat-generating member to the valve member; and a first heater mounted to the heat-generating member.
In the poppet valve of the invention and having the above structure, the heat-generating member is disposed in the fixed position in the valve casing, the first heater is mounted to the heat-generating member, the heat-generating member and the valve member are connected to each other by the heat-transfer member for expansion and contraction, and the heat-generating member and the valve member come in contact with each other in opening of the valve member. Therefore, even when the valve member is at the closed position or at some midpoint in the opening/closing operation and is at a distance from the heat-generating member, the valve member is constantly heated through the heat-transfer member and adhesion of the product from the working fluid can be prevented reliably. When the valve member is at the open position and a large amount of working fluid circulates through the flow path, the valve member comes in contact with the heat-generating member and is further and directly heated by the heat-generating member. Therefore, heating efficiency is increased and a product adhesion preventing effect is enhanced.
According to the poppet valve of the invention, in spite of a structure in which the heater for heating the valve member is disposed at the place other than the valve member, the valve member can constantly be heated by the heater irrespective of the open/closed position of the valve member. Moreover, it is possible to avoid problems such as an increase in a driving force for opening and closing and a degradation in responsiveness due to an increase in weight of the valve member, the problems occurring in a conventional product in which a heater is directly mounted to a valve member.
According to a detailed structural example of the invention, a cylindrical heat receiving member surrounding the rod and having a heat-transfer property is mounted to a back face of the valve member, a heat receiving face with which the heat-transfer face of the heat-generating member comes in contact is constituted at a tip end of the heat receiving member, and the heat-transfer member is connected to the heat receiving member and the heat-generating member.
According to another detailed structural example of the invention, the heat-generating member is in a cylindrical shape and disposed concentrically around the rod and the first heater is mounted in the heat-generating member.
In the invention, it is preferable that the heat-transfer member is in a shape of a bellows or a coil.
According to yet another detailed structural example of the invention, a bellows is provided between a partition at an end portion of the valve casing and the valve member to surround the rod and the heat-generating member, the heat receiving member, and the heat-transfer member are housed in the bellows.
In the invention, the valve casing may include a second heater.